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Another Arris SB8200 slow download performance problem

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Another Arris SB8200 slow download performance problem

I recently upgraded to the Gigabit tier and purchased an Arris SB8200 to take advantage of it. As with a number of other posters on this board, the device syncs up with 32 channels of DOCSIS 3.1 download (blue light) and 4 channels of DOCSIS 3.0 upload (green light). The upload performance relative to my old 250 Mbps service was a big improvement - went from ca. 6-7 Mbps to around 40. But the download performance is exactly where the old service was, about 330 Mbps in Xfinity speedtest.

 

While there have been a bunch of other posters with similar problems, AFAICT nobody actually has provided a solution to the issue - some of them seemed to just live with it, others to replace the modem with a different model. I've talked to Xfinity service multiple times (after the obligatory reboot-the-modem-multiple-times hoop we're forced to jump through), but while they're all perfectly nice, they're also all perfectly useless - I keep asking if they can confirm that the service is not being capped at their end, and they say there's no sign of that (possibly the most annoying part of this is that they keep sending me letters telling me my modem isn't taking full advantage of my service - gee, thanks, guys).

So coming here in the hope of some useful advice. For reference, the modem is normally talking to a gigabit router (ASUS TM-AC1700) and that to my home network of Linux machines, all hardwired with Cat6. I routinely achieve internal transfer speeds around 850 MBps so that's not a limit. I've experimented with directly coupling one machine to the modem with no noticeable improvement.

Dump of the modem connection state follows. Any advice appreciated.



The status listed show the connection state of the cable modem. They are used by your service provider to evaluate the operation of the cable modem.

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 477000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK
Security Enabled BPI+
DOCSIS Network Access Enabled Allowed  

 
Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
12 Locked QAM256 477000000 Hz -6.6 dBmV 42.0 dB 4728 423
13 Locked QAM256 483000000 Hz -6.6 dBmV 42.3 dB 4840 396
14 Locked QAM256 489000000 Hz -6.9 dBmV 42.1 dB 4749 370
15 Locked QAM256 495000000 Hz -6.8 dBmV 42.1 dB 4838 374
16 Locked QAM256 507000000 Hz -6.8 dBmV 42.0 dB 4724 359
17 Locked QAM256 513000000 Hz -7.0 dBmV 42.1 dB 4685 363
18 Locked QAM256 519000000 Hz -6.9 dBmV 42.0 dB 4608 384
19 Locked QAM256 525000000 Hz -7.0 dBmV 41.9 dB 4597 384
20 Locked QAM256 531000000 Hz -7.3 dBmV 41.9 dB 4654 390
21 Locked QAM256 537000000 Hz -7.3 dBmV 41.7 dB 4569 366
22 Locked QAM256 543000000 Hz -7.3 dBmV 41.7 dB 4734 367
23 Locked QAM256 549000000 Hz -7.2 dBmV 41.8 dB 4634 344
24 Locked QAM256 555000000 Hz -7.5 dBmV 41.5 dB 4532 359
25 Locked QAM256 561000000 Hz -7.7 dBmV 40.2 dB 5018 358
26 Locked QAM256 567000000 Hz -8.1 dBmV 40.1 dB 5340 384
27 Locked QAM256 573000000 Hz -8.3 dBmV 40.8 dB 4799 355
28 Locked QAM256 579000000 Hz -8.1 dBmV 41.2 dB 4583 324
29 Locked QAM256 585000000 Hz -8.2 dBmV 41.0 dB 4477 356
30 Locked QAM256 591000000 Hz -8.3 dBmV 40.9 dB 4564 337
31 Locked QAM256 597000000 Hz -8.3 dBmV 41.0 dB 4361 330
32 Locked QAM256 603000000 Hz -8.5 dBmV 40.3 dB 4467 359
33 Locked QAM256 609000000 Hz -8.8 dBmV 40.5 dB 4430 378
34 Locked QAM256 615000000 Hz -9.0 dBmV 40.0 dB 4366 370
35 Locked QAM256 621000000 Hz -8.9 dBmV 39.9 dB 4429 355
36 Locked QAM256 627000000 Hz -8.8 dBmV 40.3 dB 4393 322
37 Locked QAM256 633000000 Hz -8.8 dBmV 39.6 dB 4462 375
38 Locked QAM256 639000000 Hz -9.1 dBmV 39.9 dB 4396 334
39 Locked QAM256 645000000 Hz -9.3 dBmV 40.0 dB 4468 351
40 Locked QAM256 651000000 Hz -9.9 dBmV 39.7 dB 4596 367
41 Locked QAM256 657000000 Hz -9.9 dBmV 39.4 dB 4531 367
42 Locked QAM256 663000000 Hz -9.7 dBmV 39.7 dB 4406 356
48 Locked Other 850000000 Hz -14.5 dBmV 34.2 dB 886313 367



 
Upstream Bonded Channels
Channel Channel ID Lock Status US Channel Type Frequency Width Power
1 17 Locked SC-QAM Upstream 17300000 Hz 6400000 Hz 49.0 dBmV
2 18 Locked SC-QAM Upstream 23700000 Hz 6400000 Hz 49.0 dBmV
3 19 Locked SC-QAM Upstream 30300000 Hz 6400000 Hz 50.0 dBmV
4 20 Locked SC-QAM Upstream 36700000 Hz 6400000 Hz 51.0 dBmV



 

Current System Time: Sat Oct 19 05:42:58 2019

Diamond Problem Solver

Re: Another Arris SB8200 slow download performance problem

Your downstream levels are low and out of spec on a few channels. Your upstream is high and almost out of spec. However you have the cable for internet positioned, it needs to be first in the chain. It may not be the solution but a necessity before calling in or having a tech out to troubleshoot

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Expert

Re: Another Arris SB8200 slow download performance problem

Is this with a WiFi connection ? If so, for a test, does a computer hardwired directly to the 8200 cable modem (no router in the mix) have the same problem ?



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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